Fire detection system



Oct. 30, 1945; F. c. EVANS 7 2,387,752

FIRE DliTEcTI'oN SYSTEMS Filed Nov. 22, 1940 2 Sheets-Sheet 1 INVENTORF. C. EVANS BY %%,M

ATTORNEY Oct. 30, 1945. c; EVANS 2,387,752

FIRE DETECTION SYSTEMS Filed Nov. 22, 1940 2 Sheets-Sheet 2 FIG.

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\ INVENTOR I F C. EVANS BY 44M ATTORNEY Patented Oct. 30, 1945 FIRE DE ES S E Francis 0. Evans, Dongan Hills, N. 16., assignon to AmericanDistrict Telegraph Company, Jersey. City, NJ. 1., a-corporation of NewJersey Application November 22, 1940, Serial No. 366.514

6 Claims.

This invention relates generally to fire detection systems and moreparticularly to systems adapted for detecting fire in structures such asrailway bridges, round houses, or any other wooden structures. which areso located that they are normally not supervised and are subject tounusual temperature conditions or fire hazards.

- All railroad bridges, even those the main supporting structure ofwhich is steel, include wooden ties for supporting the track and woodentie supports. Because of the characteristics ofthe preservativescustomarily used in railroad ties or other wooden supporting structure,the fire hazard is unusually great, since steam locomotives dischargehot coals on the track bed and electric locomotives frequently igniteties because of elece tric sparks from third rails or sparks from therails resulting from application of the brakes. In the case of steamlocomotives, the discharge of ashes. or hot coals results in anaccumulation of inflammable materials, on the ties and their supportswhereby a fire may be started if and when favorable conditions occur.When fires start on isolated bridges or trestles, they frequently gainconsiderable headway before being discovered and after discovery it isusually impossible to reach the fire with fire extinguishing equipmentsufficient to control a large fire. Thus, it is extremely important todetect fire conditions in railway structures for the purpose ofnotifying the proper authorities and facilitating control of the firebefore it has reached dangerous proportions.

Fire detection on railway structures is a difficult problem for thereason that the track and a sizable proportion of its support is subjectto extreme ranges oi temperature both from the effects of the sun andfrom standing locomotives. It has been found that the temperature underthe fire box of a standing locomotive may rise very rapidly to as highas 210 F. This change of temperature occurs along or between the tracksat the very point where fire is most likely to occur, thereby renderingthe selection of detecting apparatus very dimcult. Rate of riseequipment is not suitable since temperature changes occur at rapidrates. The usual form of fixed temperature thermostats are also notsuitable, since they do not afford continuous supervision over extendeddistances or areas in Outdoor locations such as those of railwaybridges.

-Railway structures also render fire detection extremely difiicultbecause of vibration resulting from passing trains, vibration of thetrack and ties frequently involving amplitudes up to two inches. Thisnecessitates the. use oi a fire detecting element which can be supportedin such a manner that it is not flexed to the extent thatcrystallization will cause failure or change in operating temperature. Afurther difiiculty. arises due to physical blows resulting from fallingobjects or the passage or track walkers.

Accordingly, the principal object of this invention is to provide a firedetection system for use in railway structure A further object of thisinvention is to provide a fire detector capable 0i supervising fireconditions on railway structure where continuous supervision e subs nial d s a c s is n e sary.

Another object of this invention is to provide a. fire detector capableoi withstanding extreme distortion resulting from vibration.

Still another object of this invention is to provide a fire detector fordetecting fire conditions on outdoor structures in spite of temperaturechanges of extreme latitude and high rates.

A still further object of this invention is to provide a fire detectionsystem adapted for use on ra l y s ru u Y A still further object of thisinvention is to provide an adequately supervised signaling system o usein onn ion w h the detection p ratus which is capable of withstandingextreme amplitude of vibration and affording continuous fire supervisionover long distances under out.- door conditions.

Further objects and advantages of the invention will be apparent to.those skilled in the art after consideration of the followingspecification taken in connection with the accompanying drawingswherein:

Fig. 1 is a plan view of a section of railway bridge together with thetracl; and fire detecting equipment;

Fig. 2 is a cross section of Fig. 1 tak n on line Fig. 3 i a perspectiveview illustrating the construction of the fire detecting equipment; and

Fig. 4 is a circuit diagram illustrating the connections of signalingequipment to the fire detecting equipment shown in Fig. '1.

Figs. 1 and 2 illustrate a fire detector supported on a bridge inaccordance with the preferred form of the invention. The bridgestructure is typical of railway bridge construction and is shown by wayof example only. The track support rests upon steel members i which maybe secured to the remainder of the bridge in any desired fashion.Longitudinal steel members 2 are supported y the structure I and they inturn carry a plurality of lateral track supporting beams 3. The ties 5which support rails l are fastened to longitudinal wooden beams 8. Theconstruction is further typical of all bridge construction in that guardrails 9 are provided for safety purposes. Many bridges also include awalk I I on one side of the track and also longitudinal woodenbeams l2.

From the above description it is apparent that even steel bridgesinclude inflammable materials,

vibration of the molding 20, and therefore this element is constructedof Wood. Pipe or other metallic materials are sometimes subject tocrystallization as a result of the vibration and, therefore, are usefulin very few instances. Since the molding 20 fits loosely within thebracket 22, the

' passage of heavy trains does not cause excessive and the occurrence offire not only causes destruction of the ties but also of thelongitudinal members 3 together with the steel supports I, 2 and 3. Thelongitudinal supports 8 collect ashes and coals between the ties 5 asshown in Figs. 1 and 2 at I0, this particular part of the bridgestructure being that which is most likely to become ignited from passinglocomotives.

In view of the fact that the origin and occurrence of fires can besubstantially localized to the longitudinal wooden supports 8, it isessential that the fire detector be located as near as possible to thisarea where fires have been found most likely to start. This area is alsoimportant for the reason that the fire should be detected before seriousentire length of track is protected. Other forms of fixed temperaturefire detectors necessarily leave unprotected areas when used in outdoorstructures such as bridges.

As illustrated in Fi s. 1 and 2, the occurrence of a fire between theties 5 will immediately cause the detectors IE to operate, and inaddition,- if burning cigarettes or other materials cause a fire tostart in the walkway l I or in any other part of the structure, thedetector l5 will eventually be operated from spread of the fire alongthe vertical surfaces of the ties 5, these surfaces being the initialones to become ignited.

Fig. 3 illustrates the construction of the fire detector which comprisesfire detecting conductors l1, molding 20, and flexible insulatingcompound 23. The fire detecting wire I! consists of a fusible materialwhich should preferably melt at a temperature in the neighborhood of 400F. whereby a safe margin over the melting temperature of the insulatingcompound 23 is obtained. The insulating compound 23 is preferablyselected to have a melting temperature in the neighborhood of 250 to 275F. which gives a safe margin over the maximum ambient temperaturesoccurring under standing locomotives, this temperature beingapproximately 210 F. The fire detecting wire H has a rosin core l8 whichvaporizes to allow an actual break in the wire to occur more readilywhen the fusing temperature is reached. If the wire were solid, itwould'probably melt in such a way that the circuit would not be broken,the wire merely losing its form.

The molding I5 and the detecting wire supported thereby extendslongitudinally along the track, as illustrated in Fig. 1, and issupported by means of the brackets 22, the brackets 22 being of suchdimensions that molding l5 fits very loosely therein. It has been foundthat vibration occurring upon the passage of heavy trains may cause anamplitude of the order of two inches in flexing of the molding and doesnot subject the fire detecting wire I! to high frequency vibration orstretching, thereby preventing change of fusing temperature, falsealarms or other troubles.

Upon the occurrence of a fire the insulatin compound 23 is melted attemperatures of 250 to 275 F., whereupon the fire detecting wire I!becomes exposed to air temperatures. If the temperature continues torise, the wire I! melts at approximately 400 F., thereby breaking thealarm circuit to initiate a fire alarm.

-The alarm circuit is illustrated in Fig. 4 of the drawings andcomprises two parallel runs of fire detecting wire H. To explainfurther, between the rails of each track there are two runs of the firedetector 15, each including two fire detecting conductors I'I. Theseconductors are connected together at their mid-point, usually at one endof the bridge, by means of resistances 25 and are connected across thebattery 21 in parallel through resistances 28 at one side of battery 21and through the coil of trouble relay 30 at the other side of battery21. Relay 30 is differentially wound and, therefore, normallydeenergized, maintaining the circuit of trouble alarm bell 31 open.Relay 30 is connected at the mid-point of its coil to the normallyenergized slow-acting alarm relay 33 and normally open reset push button35. The alarm relay 3B is connected across battery 21 through contact 33of relay 33, and normally open push button 35 is normally shunted bycontact 39 of relay 33. Alarm is connected through a battery to thenormally open contacts of relay 36, and this circuit may also operatethe block signals of the railway signaling circuit.

It will be obvious from the drawings that the occurrence of fire meltsthe insulating compound 23 and both of the fusible conductors l'l. Relay30 being differentially wound, a break in both conductors of thedetection circuit has no effect on alarm 3|, and relay 33 becomesdeenergized and opens its contacts 38 and 39. Relay 36 thereupon becomesdeenergized and operates the alarm 40, and in addition it may alsooperate train signals in the block signaling system. When the firecondition has been controlled and the ruptured conductors l1 repaired,the cir cuit is restored to normal by closing the alarm circuit at pushbutton 35, thereby reenergizing relay 33 and closing contacts 38, 39 toreenergize relay 35.

If the alarm circuit should become grounded between one of theconductors l1 and ground, there would be no false alarm, since theentire circuit is not grounded. Therefore, no trouble signal for thiscondition is necessary. If two grounds in one of the conductors I!should occur on the same side of resistor 25, there would still be nofalse alarm and no trouble signal. If two simultaneous grounds occur,one on each side of resistor 25, this resistor becomes short-circuitedand current in one detector wire becomes greater than that in the other,causing an unbalance in relay 30 which closes the trouble circuitthrough alarm 3|. However, since relay 30 is differentiall wound, thealarm circuit remains closed, and alarm relay 33 is not operated. If ashort circuit occurs between the conductors l1, there is no change incurrent flowing through relay 33, and therefore no false alarm results.It will be obvious that the circuit can always operate to cause an alarmwhen the fire detecting conductors simultaneously fuse and break thealarmcircuit. This is true except in the case where the fire occursbetween two grounds existing on a single conductor, in which case theother conductor melts and relay 30 becomes unbalanced to initiate atrouble signal.

It will be obvious that any form of fire detecting wire may be used solong as it operates at a temperature above the safe ambient temperatureswhich normally occur along the railroad track. It is preferred, however,that a rosin core wire consisting of an alloy composition of lead, tin,antimony, and bismuth be used. Any form of insulating compound 23 issuitableso lone as it remains flexible under ambient temperatures andmelts at approximately 275 F. This mate rial preferably consists of arubber content mastic which never becomes brittle under ordinaryatmospheric conditions.

The bridge structure illustrated in the drawings is shown by way ofexample only, the invention being applicable to all types of bridges orother wooden and steel structures such as round houses or road beds.Therefore, the invention should not be limited to the particularconstruction illustrated in the drawings. Any form of bracket issuitable for supporting the molding 20 so long as it is so constructedthat the molding will have a sufficient degree of movement to preventrupture of the molding or conductors IT or crystallization of theconductors.

From the above description it is evident that this invention provides afire detection system which is particularly adapted for use inconnection with railway track supporting structures. The system is notaffected by normal ambient temperatures occurring along the road bed,and it is not affected by physical impact from falling objects or othercauses. Furthermore, the particular form of fire detector continuouslysupervises any desired length of track together with its supportingstructure, whereby fire may be detected in the inherently inaccessibleareas which are characteristic of railroad bridges. Detection occursbefore serious fire conditions can arise whereby simple forms of fireextinguishing equipment are adequate to extinguish the fire. Thearticular form of detector and its supporting bracket eliminatesinjuries resulting from the excessive vibrations caused by the passageof heavy high speed trains.

It is not intended that the invention shall be limited to the formillustrated in the drawings, since various modifications will be obviousto those skilled in the art, and therefor it is desired that theinvention shall be limited only by the appended claims as required bythe scope of the prior art.

I claim:

1. The combination with inflammable supporting structure subject tovibration of a fire detector comprising runs of wood molding, a pair offusible electrical conductors within each run of said molding, theconductors being connected to one another, and brackets on theinflammable supporting structure surrounding said molding for attachingthe molding to said structure against separation therefrom and forloosely supporting the molding whereby vibration does not causeexcessive flexing of the molding and conductors.

2. The combination with inflammable supporting structure subject tovibration of a fire detector comprising two substantially parallel runsof wood molding, a fusible electrical conductor within each run of saidmolding, the conductors being connected to one another, and brackets onthe inflammable supporting structure surrounding said molding forattaching the molding to said structure against separation therefrom andfor loosely supporting the molding whereby vibration does not causeexcessive flexing of the molding and conductors.

3. The combination with inflammable supporting structure subject tovibration of a fire detector comprising a run of wood molding, a fusibleelectrical conductor within said molding, and brackets on theinflammable supporting structure surrounding said molding for attachingthe molding to said structure against separation therefrom and forloosely supporting the molding whereby vibration does not causeexcessive flexing of the molding and conductors.

4. A fire detecting device for affording continuous supervision of fireconditions along its length comprising a Wood molding, a fusibleelectrical conductor within a groove in said molding, and sealing meansfor protecting said fusible electrical conductor from the effect oftemperature changes and mechanical shock including a flexible materialin said groove which is fusible at a lower temperature than saidconductor whereby the occurrence of a predetermined temperature in thevicinity of said molding melts the sealing means and exposes saidfusible conductor to the dangerous temperature.

5. A fire detecting device for affording continuous supervision of fireconditions along its length comprising a flexible molding, a fusibleelectrical conductor within said molding, and sealing means forprotecting said fusible electrical conductor from the effects oftemperature changes and mechanical shock including a plastic materialwhich is fusible at a lower temperature than said conductor whereby theoccurrence of the predetermined temperature in the vicinity of saidmolding melts the sealing means and exposes said fusible conductor to adangerous temperature.

6. A fire detecting device for affording continuous supervision of fireconditions along its length comprising a support, a fusible electricalconductor within said support, and sealing means for protecting saidfusible electrical conductor from the effects of temperature changes andmechanical shock including a material which is fusible at a lowertemperature than said conductor whereby the occurrence of thepredetermined temperature in the vicinity of said support melts thesealing means and exposes said fusible conductor to a dangeroustemperature.

FRANCIS C. EVANS.

